The present invention relates to a paper-drive type automatic drafting machine used as a peripheral output apparatus of a computer of a CAD system and, in particular, to a rolled paper sheet feeding mechanism of such drafting machine.
According to the conventional drafting machine of this kind shown in FIG. 7 of the accompanying drawings, a rolled paper of a paper sheet 4 is rotatably held on a rolled paper holding means 12 placed below a platen 2 of the drafting machine.
When the conventional drafting machine carries out a drawing, it is necessary to perform a first step paper sheet paying-out operation which will be described below.
First, the operation arises from a condition of the rolled paper feeding mechanism, as shown in the prior art depicted in FIG. 8(A), in which the paper sheet 4, of the rolled paper is wound around a rolling means 16 such that a slack portion of the rolled paper does not exist below the rolled paper supporting means 12. Beginning with this condition, the drive roller 6 is driven counterclockwise, and the paper sheet 4 is paid out from the rolled paper onto the platen 2 and a part of the rolled paper supported on the supporting means 12, which corresponds to that of a drawing, is pulled out. As a result, part of the rolled paper is hung below the rolling means 16 as shown in FIG. 8(B).
Next, the drive roller 6 is driven to rotate in the reverse direction or clockwise by a number of rotations that equals that of the previous counterclockwise rotation such that a part of the paper sheet 4 is hung down below the rolled paper supporting means 12 as shown in FIG. 8(C).
After this paper sheet paying-out operation is performed, the drive roller 6 reversibly turns based on drawing data of a host computer and the paper sheet 4 is reciprocated in a front-and-rear direction on the platen 2, such that a writing instrument 10, while moving transversely acrossing the platen 2, controllably touches the paper sheet 4 on a drawing roller 9 in order to carry out a drawing operation.
After the drawing operation, the motor 18 is driven in order to roll up a drawn paper sheet 4 on the rolling means 16 finishing a whole operation of one drawing.
By repeating a series of steps starting from the sheet paying-out step, it is possible to continuously carry out drawings.